1. Field of the Invention
The present invention relates to a portable terminal. More particularly, the present invention relates to a method for providing a push to talk (PTT) communication service using abbreviated numbers.
2. Description of the Related Art
Typically, a conventional wireless communication system for the portable terminals has a plurality of small unit areas or cells divided or distributed in the whole service coverage area. Each of the cells has a base station (BS) located therein such that the corresponding BS can cover its corresponding cell. All the base stations are centrally controlled by a mobile switching center (MSC) so that subscribers may maintain their calls in the coverage area when moving between cells.
According to advancements in communication technologies, several solutions are provided for combining an internet protocol (IP) network with a wireless communication network for portable terminals. One such solution is, for example, voice over IP (VoIP) which provides a voice service based on packets using IP.
A conventional call service based on these packets has a defect because call establishment time is relatively greater in order to establish the call through both the wireless communication network and the IP network. In order to overcome such a defect, the conventional call service system provides an interactive call service such as a group call and a private call by using a multicast function of IP network. The interactive call service is a type of call in which traffic comprises inter-actions between a plurality of users. Such a call has, for example, a function of push to talk (PTT) as in a Walkie-Talkie. The group call mentioned above provides a conference call between some users selected among the predetermined users group, and the private call provides a one-to-one call between the users selected among the predetermined users group.
Such a PTT communication service is capable of providing voice and data services to a plurality of users or users group such that the users can express their own intentions or what they want to say by pressing predetermined buttons for PTT communication while the users' terminals or the portable terminals capable of performing the PTT communication service transmit service requests to the related network. Then, the network rejects the service requests or accepts the service requests and assigns the requested resources to the corresponding users based on predetermined determination criteria such as the availability of the existing resources thereof and priorities of the, requesting users, which have sent the service requests. At the same time, the requesting users are connected with all the other active users which belong to a specific subscriber group by establishing the connection in the network system. Accordingly, the requesting users can talk with the other parties who then hear from the requesting users on the corresponding channel if a voice connection is established. If the users want to release the request of the PTT communication service, the corresponding portable terminals send the network release messages to the network to release assignment of the resources provided to the users. Such a conventional PTT communication system can provide a point-to-point communication service as well as a point-to-plural-points communication service.
The PTT portable terminal, however, needs several steps to perform PTT communication service. Specifically, if the user selects some menu corresponding to PTT communication service mode, or the user inputs some mode keys of PTT communication service on the portable terminal, the user receives a list of subscribers of the PTT communication service which belong to a specific group (hereinafter, the subscriber will be referred to as “buddy”) from the network. Then, the user retrieves and searches the received buddy list, selects a certain buddy or buddies to whom the user wants to be connected, and executes the desired PTT communication. Therefore, several steps for key inputs and menu selections are required to establish a PTT communication service in the PTT portable terminals, which cause inefficient use of time and tediousness in operating of the PTT terminal.